1. Field of the Invention
This invention relates to apparatus for tensioning a threaded stud or the like such as is used in making up a flanged joint in pressure lines and pressure vessels, or other environment in which control of stress in threaded fasteners is desired.
2. Description of the Prior Art
Flanged joints in various pressure lines and pressure vessels are widely used in industry. Two parts, typically of cylindrical shape, are manufactured with annular flanges at their ends. The flanges are formed with congruent hole patterns. The two members are joined to one another in a pressure tight manner by first introducing a gasket between the two flanges and then by joining the flanges with threaded stud-like members, e.g., studs, bolts or stud-bolts, which extend through the holes and have nuts engaged therewith. The term "stud" is sometimes used herein for convenience to refer to the broader class of stud-like members to which the invention applies. It is important, particularly in large diameter members, that the tension in the studs be sufficient to withstand imposed forces and be uniform so as to avoid deformation of the flanges and the members to which they are fixed.
A device for tensioning studs in the above described environment is disclosed in U.S. Pat. No. 3,015,975. The patented device includes a hollow tubular housing that fits over the stud and the nut and rests on the surface of the flange. There is a puller bar which has at one end an interiorly threaded collar adapted for engagement with the portion of the stud that protrudes beyond the nut. The puller bar collar is engaged with the stud threads by rotating the puller bar, and there is a hydraulically powered mechanism to which the remote end of the puller bar is fastened. When the hydraulic mechanism is actuated, tension is applied to the stud so that the nut can be tightened, the amount of the tension being controlled by controlling the hydraulic pressure applied to the hydraulic actuator. Devices similar to that referred to above are also shown in U.S. Pats., Nos. 2,866,370; 3,158,015; 3,162,071 and 3,285,568. Substantial commerce exists in such devices, and they are widely used, particularly where flanged joints of large diameter are employed. Formation of a flanged joint is a time consuming procedure, however, because the puller bar must be engaged and disengaged with each stud several times, and engagement and disengagement is a time consuming procedure because the puller bar must be rotated numerous revolutions each time it is engaged with or disengaged from the stud threads.
U.S. Pat. No. 3,995,828 discloses bolt tensioning apparatus having a segmented nut and a mechanism for moving the segments between a radially inward position at which they engage the stud and a radially outward position at which they are free of the stud. The apparatus disclosed in the U.S. Pat. No. 3,995,828 eliminates the necessity to rotate the puller bar through numerous revolutions each time the apparatus is engaged with or disengaged from the stud. Although the device disclosed in the U.S. Pat. No. 3,995,828 reduces the time necessary for engagement and disengagement with the stud, the apparatus requires an unduly long stud because a longitudinally or axially moving sleeve is employed in moving the segments radially. Longitudinal movement of the sleeve requires substantial space between the segments and the longitudinal housing that contains the segments. Consequently, the patented device is useful only on unduly long studs which are undesirable as are the special studs provided with concentric grooves that are specifically disclosed in the U.S. Pat. No. 3,995,828.